Nozzle



$94,692 NozzLE James D. Ledbetter, Cedar Grove, Hartmann J. Kircher III, Sparta, and Raymond I. Novotny, Rockaway, NJ., assignors, by mesne assignments, to Thiokol Chemical Corporation, a corporation of Delaware Application January 25, 1957, Serial No. 636,427

4 Claims. (Cl. 239-75) This invention relates generally to rocket nozzle structures and more particularly to a variable area rocket nozzle and actuating mechanism therefor.

The use of solid propellents in rockets and propellent devices such as tank pressurization systems and jet mixing systems is well known as are some of the inherent problems connected with such use. For example, many of the solid propellents commonly used have a burning rate which varies widely with variations in temperature.

When used in `short burning-time rockets, these solid propellents have the undesirable characteristic of a large increase in pressure as the burning time decreases with increasing ambient temperatures. As a result, variations in velocity are effected which in turn, atleet the trajectory of the rocket, and an overly heavy motor body is required. Similarly, as the ambient temperature decreases, the burning time of the solid propellent increases so that the evolution of gas is slowed and pressures are low.

The chief object of the present invention is to provide means which will compensate for the variations in the burning rate of solid propellents so as to control the gas pressures.

Another important object of the present invention is to provide means for automatically controlling the gas pressures evolved by a burning solid propellent in accordance with temperature.

A still further important object ofthe present invention is to provide automatic means for compensating for the changes in solid propellent burning rates by varying the throat area of a rocket nozzle in accordance with ambient temperature.

Other objects and advantages of the present invention will become apparent during the course of the following description. Y

In the drawings we have shown two embodiments of the invention. In these showings:

Figure 1 is an end elevational View of a rocket nozzle embodying the invention;

Figure 2 is a central, longitudinal sectional view thereof taken on the line 2 2 of Figure 1;

Figure 3 is a vertical sectional View taken on the line 3-3 of Figure 2 showing some of the throat area varying restrictors, parts being shown in elevation;

Figure 4 is a fragmentary, vertical sectional view taken on the line 4-4 of Figure 2;

Figure 5 is a fragmentary, vertical 'sectional view taken on the line 5 5 of Figure 2; and

Figure 6 is a fragmentary, sectional View of another embodiment of the invention.

In its broadest aspects, the present invention contemplates the positioning of a thermally sensitive actuator in the region of the propellent chamber to sense the ambient propellent temperature and adjust the nozzle area before tiring of the rocket to control the gas pressures when tired.

Referring to the drawings, numeral 10 designates a rocket motor body fixed at its rear end to a nozzle body 12. The motor body includes a nozzle section 14 in- 2,894,692 Patented July 14, 1959 wardly spaced from the motor body wall and formingY therewith a chamber 16.

The front face 18 of the nozzle body 12 is spaced from the rear edge of the nozzle section 14 to provide an annular recess therewith for the reception of a cam ring 20 which is inserted during assembly, and is also provided with a plurality of circumferentially spaced pockets 22 opening onto the recess and radially inward on the nozzle section 24 in the nozzle body 12.

A nozzle restrictor 26 is rockably mounted in a recess 28 in each of the pockets 22 and their inner surfaces conform to the nozzle throat 24. The forward faces of the restrictors 26 are each provided with a lug or pin 30' which projects through one of a plurality of arcuate slots 32 formed in the cam ring 20 and spaced circumferentially thereabout. Inasmuch as the radius of curvature of the slots 32 does not pass through the center of the ring 20 upon its rotation the slots act as cams on the restrictor pins 30 to pivot the restrictors 26 inwardly about their mounting recesses 28 to decrease the nozzle area.

Rotation of the cam ring '20 in either direction as limited by the lengths ofthe slots 32 is effected by means of a thermostatic bimetal actuator 34 spirally arranged in the chamber 16 and having an end fixed to a cam ring pin 36 and the other end fixed to the nozzle body 12 by pin 11. As the ambient temperature increases or decreases, the thermostatic bimetal actuator 34 deilects thereby tightening or loosening the spiral and moving pin 36 in an arcuate path to rotate the cam ring 20 and etfect movement of the nozzle segments or wings 26 to vary the throat area.

The nozzle body 12 is closed at its rear by a flat closure 46 of resilient plastic such as polyethylene which is held in position by forcing it over the end of nozzle 12 as shown in Figure 2. When the rocket is tired, the gases exert pressure on *the closure 46 and the cover is blown olf.

It will now be readily apparent that if the ambient temperature is high, the thermostatic bimetal actuator 34 will open the nozzle area to its maximum (Figure 4) allowing, when tired, the high pressures of the rocket motor to be relieved to the nominal operating pressure desired.

Conversely, if the ambient temperature is low, the actuator 34 will reduce the nozzle area and upon tiring, permit a buildup of pressure to the desired operating pressure. Thus the desired velocities and predictable trajectories may be obtained. Moreover, from a structural standpoint, the motor body weight may be decreased thereby effecting a substantial saving in material and cost per unit.

The embodiment of the invention disclosed in Figure 6 is similar to that described except for the mounting of the thermostatic bimetal actuator 45 which is positioned in and along the axis of the nozzle body 12. The closure 38 is mounted on a central shaft 41 to which the innner end of the actuator 45 is fixed, the outer end being connected to an apertured rod 44 which is hooked over a shear pin 42.

The nozzle area is controlled as before and when the rocket is red, both the closure plate 38 and the actuator 45 are ejected rearwardly by the high velocity gases.

It will now be apparent that the apparatus comprising the invention will automatically compensate for the changes in the burning rates of solid propellents with temperature by regulating the nozzle throat area as a function of temperature with resultant economies in weight and cost and more predictable velocities and tra jectories.

It is to be understood that the forms of the invention herewith shown and described are to be taken aspreferred examples of the same and that various changes may be made n the shape, size and arrangement of 1. An apparatus for varying theA throat area of a nozzle bo'dy having a plurality of circumferentially spaced, axially extending recesses formed therein and opening on the throat area thereof,.comprising a plurality of restrictors arranged in and lling the recesses and keach having an end pivotally mounted in a recess, an annulus rotatably mounted in the nozzle body and having its inner periphery flush with and forming a part of the nozzle throat area adjacent said restrictors, said annulus having a plurality of circumferentially spaced, cam slots formed therein, and a pin formed on the other end of each of said restrictors and projecting into one each of the cam slots whereby rotation of said annulus eiects pivoting of said restrictors radially into and out of the nozzle throat area.

2. An apparatus as recited in claim 1 wherein thermostatic means are connected to the nozzle body and to said annulus to rotate the latter to etect automatic adjustment of the nozzle throat area in accordance with changes in ambient temperature.

3. An apparatus as recited in claim 2 wherein a stud is xed to and projects radially inward from said rotatable annulus, a nozzle closure including an axially eX- tending shaft is mounted against the rear of said nozzle body, and said thermostatic means is xed to said shaft and connected to the stud to retain the closure in position and to rotate said annulus upon expansion and contraction.

4. An apparatus as recited in claim 2 wherein the nozzle body includes an annular chamber surroundingV and concentric with the nozzle throat area and open toward and closely adjacent said annulus, a stud is xed to and projects axially from said rotatable annulus into the chamber, and said thermostatic means is positioned in the. chamber and connected to the stud and to a wall of the chamber to rotate said annulus upon expansion and contraction.

References Cited in the le of this patent Y UNITED STATES PATENTS Skinner u- Oct. 7, 1952 2,669,834 Helms Feb. 23, 1954 FOREIGN PATENTS 623,163 France Mar. 14, 1927 

